Improvement in burglar-alarms



HENRY HoLcRoFTQ Improvement nBurglar Alarms.

No. 124,356. f Patented Mafchm-fg. 1

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UNITED STATES ATENT CFFICE.

HENRY HOLCROFT, OF MEDIA, ASSIGNOR OF TWO-THIRDS OF HIS RIGHT TO WILLIAM A. CHADWIGK AND JAMES Gr. KITCHEN, OF PHILADELPHIA,

PENNSYLVANIA.

IMPROVEMENT IN BURGLAR-ALARMS.

Specification forming part of Letters Patent No. 124,356, dated March 5, 1872.

Specification describing certain Improvements in Burglar-Alarms, invented by HENRY HOLCROFT, of Media, Delaware county, and State of Pennsylvania.

The rst part of my invention consists in a forked spring for suspending the alarm to the spindle of a door-knob. The second part of my invention relates to the combina-tion of a cylinder or drum, a cord, weight, and hook for operating the hammer of the gong.

Figure 1 is a side elevation of a machine embodying my invention. Fig. 2 is a front elevation of the same with the gong removed to show the hammer. Fig. 3 is a Vertical transverse section of the gong, spindle, drum, and frame.

Similar letters in the drawing refer to like parts.

A is the fork-shaped spring, which should be made of good spring-steel, and made the shape as shown in the drawing, with circular notches at the top; and from these notches in each prong it tapers out on the inside to each end. f is la frame, which may be made of brass or iron, and is fastened to the fork A. Into this frame is fitted the spindle F. On this spindle is fastened the drum d and gong B, and also the small cam-wheel, containing four teeth, c c c e. (See Fig. 2.) E is the hammer. One end is pivoted on a stud fastened to frame f. The arm of the hammer rests on the small cam-wheel. The working of this hammer may be assisted by a small elliptic spring fastened to the frame f, and resting on the arm of the hammer E. C is the cord. One end is fastened to the drum d; the other end to the weight D. At the top of the weight is a hook, h. Atthe bottom of the frame j' is a hook, s.

The operation is as follows: To set the alarm, the forked spring is forced on the spindle of a door-knob, (on the inside of the room.) The spring will cause it to grasp the spindle and hang vertical. The cord is then wound around the drum (1 and the hook of the weight is hooked on the. hook s of the frame f. Should the knob on the outside of the door be turned in an effort to open the door, it will move the frame f out of a vertical line, when the weight D will slip oi' the hook s, and the gravity of the weight drawing the cord C will revolve the drum and cam-wheel, and the teeth e e e e will cause the hammer E to strike the gong in rapid succession, giving the alarm and continuing till the weight has drawn all the cord off the drum.

Claims.

I claim- 1. The spring A, when used in combination withV the spindle of a door-knob, for the purpose of suspending the alarm, as shown and above described.

2. I claim the combination of the drum d, cord c, weight D, and hooks s and h, for operating the hammer, as above described.

' H. HOLCROFT.

lVitncsses: f

FRANK BoUTCHnR, WM. A. CnADwIcK. 

